Analysis Of Bacterial And Fungal Community Structure In The Recirculating Nutrient Solution Of Tomato Plug Seedlings Under Ebb-and-flow Irrigation

Under ebb-and-flow irrigation,the tomato variety ‘Zhongza105' was taken as materials to raise seedlings in plug during summer and winter.Firstly,the optimum irrigation height was determined,and then we investigated the composition and dynamics of microbial community in the recirculating nutrient solution and substrate of tomato plug seedling during summer and winter by mainly using high-throughput sequencing approaches based on the optimal irrigation height.The main results were as follows:1.Under different feeding height(1 cm,2 cm and 3 cm),by comparing the seedling growth indexes,root vigor,as well as the water and fertilizer use efficiency,the suitable irrigation height was screened.The results showed that both in summer and winter,the root-shoot ratio and seedling index showed no significant difference among three irrigation heights.Under 3 cm of irrigation height,the root vigor was significantly lower than that under 1 cm and 2 cm.In summer,the water use efficiency and the nitrogen use efficiency showed highest under 2 cm of irrigation height.In winter,the water use efficiency showed no significant difference among three irrigation heights,and the nitrogen use efficiency was higher at 2 cm and 3 cm.Based on these above indexes,for tomato plug seedlings under ebb-and-flow irrigation,both in summer and winter,the suitable irrigation height was 2 cm,which could not only ensure the seedlings growth and root vigor,but also improve the use efficiency of water and fertilizer.2.In this study,we found that the population of bacteria increased with decreasing the bacteria diversity and richness during summer,while the population of bacteria decreased with increasing the bacteria diversity and richness during winter.Phylum Proteobacteria and genus Pseudomonaswere dominant in the nutrient solution during both season.There were discrepancies in the relative abundance of different genera in nutrient solutionin such a way that the relative abundance of Pseudomonas and Comamonas in summer increased and decreased respectively.Moreover,in winter the relative abundance of Sphingomonas increased;whereas it showed a decreasing trend as in case of Massilia.At species level,Comamonas testosteroni was dominant in the nutrient solution during both the studied seasons.Furthermore,we found some plant-growth promoting bacteria,such as Ralstonia pickettii whose relative abundance in both seasons increased.We also found Pseudomonas mediterranea which might be a sort of tomato pathogen,with its relative abundance increased in summer and decreased in winter.In the seedling substrate of tomato,the diversity and richness of bacteria increased during summer and winter.During the irrigation process,there were differences in the relative abundance of different genera in seedling substrate.For instance,while the relative abundance of Devosia increased during both the studies seasons,the relative abundance of Pseudonocardia decreased.At species level,we found some potential plant-growth promoting bacteria,such as Sphingomonas koreensis and Pseudomonas geniculata that existed in summer and winter seedling substrate,respectively.And their relative abundance all increased,regardless of studies seasons.In addition,Pseudomonas mediterraneawith potential pathogenicity existed in summer and winter seedling substrate,and its relative abundance increased as well.3.In this study,we found the diversity and richness of fungi to be increased during summer,while the richness of fungi had left no alteration with increasing the fungi diversity during winter.Phylum Basidiomycota and genus Amanita were dominant in the nutrient solution during both season.There were significant differences in the relative abundance of different genera in nutrient solution,such as the relative abundance of Amanita in summer increased,while the relative abundance of Alternaria and Trichoderma decreased in summer and increased in winter respectively.In addition,this parameter in bacterium Rhodosporidium decreased in winter nutrient solution.At species level,Amanita fulva was dominant in the nutrient solution during both seasons.Furthermore,some unique species such as Trichoderma harzianum have potential plant growth promoting functions with their relative abundance decreased in summer and increased in winter.In addition,we also found potential pathogenic fungi,such as Fusarium oxysporum with their relative abundance increased in summer and decreased in winter.Although the richness of fungi increased in the seedling substrate of tomato grown in summer,the diversity had no significant variation.Conversely,the diversity and richness of fungi increased in winter.Following seedling emergence,the relative abundance of Trichoderma increased during both seasons,while the relative abundance of Phaeoacremonium decreased.At species level,we found some potential plant-growth promoting fungi such as Trichoderma harzianum which the relative abundance of it increased both in summer and winter.At the same time,we also found potential pathogens,including Fusarium oxysporum and Fusarium solani which existed in summer and winter seedling substrate,respectively.And the relative abundance of the two increased.